• Title, Summary, Keyword: Fatigue

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A Study on Application of Fatigue Correction Factor for Environmental Fatigue Evaluation of Pressurizer Surge Line (가압기 밀림관 환경피로평가를 위한 피로보정계수 적용에 관한 연구)

  • Yang, Jun-Seog;Park, Chi-Yong;Kang, Seon-Ye
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.33 no.10
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    • pp.1151-1157
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    • 2009
  • Nuclear power plants applying for the continued operation over design life are required to address the effects of reactor water environment in fatigue design requirement of the ASME Code. Reactor water environmental effects are generally evaluated by calculating fatigue correction factors on fatigue usage. This paper describes the application for pressurizer surge line of environmental fatigue correction factors and the strain rate impact in the application. From this paper, the environmental fatigue correction factors resulted from the assumption of a step change in temperature are especially compared with those calculated from the data measured during plant startup. As a conclusion of this paper, the design transient conditions applied to the fatigue design may be conservative in case of the environmental fatigue evaluation.

Influencing Factors on Fatigue of Middle Aged Women (중년여성의 피로에 영향을 미치는 요인)

  • Chang, Hae-Kyung
    • Korean Journal of Adult Nursing
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    • v.22 no.6
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    • pp.634-643
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    • 2010
  • Purpose: The purpose of this study was to identify the reported factors influencing fatigue of middle aged women. Methods: Two hundred seven middle aged women between 40 and 59 years of age were recruited from five areas in Korea from March 1, 2010, to April 20, 2010. Data were collected by self-reported questionnaires. Data analysis was done using SPSS/WIN 15.0 program for descriptive statistics, Pearson correlation coefficients and stepwise multiple regression. Results: The average score of fatigue was $2.34{\pm}0.40$. There were significant differences in reported fatigue according to economic status and health status. The reported fatigue was significantly correlated with somatic attribution, psychological attribution, normalizing attribution, depression, marital adjustment, stress, and social support. The major factors that affect fatigue in middle aged women were stress, depression, and normalizing attribution, which explained 32.3% of fatigue. Conclusion: The findings can reduce the fatigue by controlling stress and depression. Additionally, this study can understand the attribution of fatigue in middle aged women. More studies are needed to identify other variables that influence on the fatigue of middle aged women.

The Degree of Fatigue According to Subjective Recognition in Middle - Aged Women - (중년여성의 피로인지여부에 따른 피로 정도)

  • Shin, Eun-Ju
    • Journal of Oriental Neuropsychiatry
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    • v.14 no.2
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    • pp.107-115
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    • 2003
  • This study was conducted to investigate the subjective degree of fatigue, the degree of fatigue depending on analysis of MMPI and SDNN in middle-aged women. Data were collected from 51 patients, registered at Oriental Medicine Hospital in J-city and K-city respectively. The instrument used in this study were the Multidimensional Assessment of Fatigue developed by Belza(1995) and revised by Jung & Kim(1999) and the Minnesota Multiphasic Personality Inventory(MMPI) and Standard Deviation of Normal to Normal(SDNN). The collected data were analyzed by SPSS/WIN 9.0 program using frequencies, percentage, mean, standard deviation, t-test. The degree of fatigue in middle-aged women: the average score 30.61 out of the total score 40. Subdivision of fatigue scores: common fatigue degree 7.71, distress due to fatigue 7.67, degree of daily activity fatigue 7.43, and fatigue frequency in the previous week 7.84. The degree of fatigue according to subjective recognition was shown significant difference(t=6.707, p=.000).: group of recognition (33.58), group of ignorance (23.47). The degree of fatigue according to MMPI was shown significant difference. : In the group of recognition, scales of Hs, D, Hy, Pt were higher. The degree of fatigue according to SDNN was shown significant difference (T=-4.062, P=.000). : group of recognition (33.47ms), group of ignorance (45.70ms). The total fatigue score and scales of Hs, D, Hy in MMPI was correlated positively (r=.576; r=.466; r=.518), and total fatigue score and SDNN was correlated negatively (r=-.576). Conclusively fatigue is one of difficult problems in middle-aged women. Therefore it is necessary to develope some nursing intervention for reducing fatigue in its early stages.

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Thermal-Mechanical and Low Cycle Fatigue Characteristics of 12Cr Heat Resisting Steel with Hold Time Effects (유지시간 효과를 고려한 12Cr 내열강의 열피로 및 저주기 피로 특성)

  • Ha, J.S.;Koh, S.K.;Ong, J.W.
    • Transactions of the Korean Society of Automotive Engineers
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    • v.3 no.1
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    • pp.1-12
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    • 1995
  • Isothermal and thermal-mechanical fatigue characteristics of 12Cr heat resisting steel used for high temperature applications were investigated including hold time effects. Isothermal low cycle fatigue test at $600^{\circ}C$ and in-phase, out-of-phase thermal-mechanical fatigue test at 350 to $600^{\circ}C$ were conducted using smooth cylindrical hollow specimen under strain-control with total strain ranges from 0.006 to 0.015. Regardless of thermal-mechanical and isothermal fatigue tests, cyclic softening behavior was observed and much more pronounced in the thermal-mechanical fatigue tests with hold times due to the stress relaxation during the hold time. The phase difference between temperature and strain in thermal-mechanical fatigue tests resulted in significantly shorter fatigue life for out-of-phase compared to in-phase. The differences in fatigue lives were dependent upon the magnitudes of plastic strain ranges and mean stresses. During the hold time in the strain-controlled fatigue tests, the increase in the plastic strain range and the stress relaxation were observed. It appeared that the increase in plastic strain range per cycle and the introduction of creep damage made important contributions to the reduction of thermal-mechanical fatigue life with hold time, and the life reduction tendency was more remarkable in the in-phase than in the out-of-phase thermal-mechanical fatigue. Isothermal fatigue tests performed under the combination of fast and slow strain rates at $600^{\circ}C$ showed that the fatigue life decreased as the strain rate and frequency decreased,especially for the low strain ranges.

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A Preliminary Study on Fatigue Strength of High Toughness Thermoplastic Composite Material AS4/PEEK (고인성 열가소성 복합재료 AS4/PEEK의 피로강도에 관한 기초적 검토)

  • Song, Ji-Ho;Gang, Jae-Yun
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.24 no.4
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    • pp.1055-1064
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    • 2000
  • First, various specimen geometries, namely, coupon type, waisted type and dog-bone type, were examined to determine appropriate fatigue specimen of thermoplastic composite material AS4/PEEK and the n, fatigue strength of smooth and notched specimens of AS4/PEEK [-45/0/+45/90]2s was investigated. Fatigue tests were performed under load controlled condition at a stress ratio of 0. 1 at a frequency of 5Hz. Stiffness degradation of specimens with fatigue cycling was monitored using an automated unloading compliance technique. The waisted type specimen is found appropriate for smooth fatigue specimen geometry of AS4/PEEK. As for the effect of stress concentration, it is found that fatigue strength is higher for a 2mm-diameter hole notched specimen than a 5mm-diameter one. Fatigue notch factor decreases with the increase of fatigue life. These results are far different from the trend of fatigue strength of metallic materials. The stiffness variation of smooth specimen was only 4% at maximum until final fracture. On the other hand, the stiffness of hole notched specimen was reduced by 45% at maximum. Notched fatigue strength was compared between thermoplastic composite AS4/PEEK and thermosetting composite Graphite/Epoxy. In long-life fatigue (>104), the AS4/PEEK composite shows superior fatigue strength, but in short-life fatigue, the fatigue strength of the Graphite/Epoxy composite is nearly equal or somewhat higher than that of the AS4/PEEK composite.

Women's Level of Fatigue after Delivery (산부의 피로정도에 관한 연구)

  • Kim, Sun-Hee
    • Korean Parent-Child Health Journal
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    • v.4 no.1
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    • pp.1-18
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    • 2001
  • Fatigue after delivery affect women's birth experience and interrupt the process of labor. Finally woman cannot have a positive birth result and will experience a postpartum fatigue. But researches about fatigue during the labor are lacked. Nurse help adapting a mother's role, bonding with new baby, recovering after birth, and improving woman's quality of life through decreasing fatigue during the labor and intercepting a continued postpartum fatigue. So it is very important that measuring a fatigue and confirming relationships between fatigue and factors affecting fatigue. The purpose of this study was measuring the level of fatigue within 4hours after delivery and identifing factors affecting fatigue. The ultimate goal was to contribute to improving a birth experience and adapting after birth through decreasing the level of fatigue and interventions. The data was collected for this study at the hospital of two universities and the third hospital in Seoul from Aug. 15. to Nov. 10. 2000. The subjects were 106 of mothers who deliveried a normal newborn and were tested within four hours after birth. The instruments were The Visual Analogue Scale for fatigue, The State Anxiety Inventory, and The Labor Support Inventory. The data were analyzed by using percentage, mean, SD, t-test, ANOVA, Pearson correlation. The results of this study were as follows; (1) The level of fatigue during the labor was 61.48point. (2) The deferences according to general and obstetric character affecting fatigue founded that there were Significant differences according to job(t=2.659, p=0.009), and the type of delivery(t=-2.035, p=0.044). (3) The deferences according to factors affecting fatigue revealed that there was significant difference according to quality of sleep(F=2.935, p=0.037). The significant fatigue and the fatigue after delivery was anxiety(r=0.343, p=0.000). The above findings indicate that the level of fatigue during the labor is higher than during pregnancy and postpartum. Woman having a job, delivering by vacuum was more fatigued. The level of fatigue according to a quality of sleep was significant difference. The poor quality of sleep, higher level of fatigue. And the more anxiety after delivery, the more fatigue. So, the variable nursing interventions for lessening the level of fatigue through appling the situation for rest, relaxation during the labor to reserve energy, and decreasing anxiety should be provided for mothers.

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Fatigue Strength Improvement and Fatigue Characteristics by TIG-Dressing on Weld Bead Toes (용접지단부 TIG처리에 의한 피로강도향상 및 피로특성)

  • Jung, Young Hwa;Kim, Ik Gyeom;Nam, Wang Hyone;Chang, Dong Huy
    • Journal of Industrial Technology
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    • v.20 no.A
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    • pp.169-178
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    • 2000
  • The 4-point bending tests have been performed In order to estimate the effect of TIG-dressing on fatigue strength and fatigue characteristics quantitatively for non load-carrying fillet welded joints subjected to pure bending. As a result of fatigue tests, fatigue strengths of as-welded specimens have satisfied the grade of fatigue strength prescribed in specifications of korea, AASHTO and JSSC. Fatigue strength at 2 million cycles of TIG-dressing specimens have increased compared with as-welded specimens. As the result of beachmark tests, fatigue cracks occurred at several points, where the radius of curvature and flank angle in the weld bead toes were low, and grew as semi-elliptical cracks, then approached to fracture. As a result of finite element analysis, stress concentration factor in weld bead toes has closely related to the flank angle and radius of curvature, and between these, the radius of curvature has more largely affected in stress concentration factor than flank angle. As a result of fracture mechanics approaches, the crack correction factor of test specimens has largely affected on stress gradient correction factor in case a/t is below 0.4. From the relations between stress intensity factor range estimated from FEM analysis and fatigue crack growth rate, fatigue life has been correctly calculated.

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Improvement of Fatigue Strength by Spot Heating for Out-of-plane Gusset (국부가열을 이용한 면외거셋의 피로강도 향상)

  • Jung, Young-Hwa;Nam, Wang-Hyone;Chang, Dong-Huy
    • Journal of Industrial Technology
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    • v.21 no.B
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    • pp.213-222
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    • 2001
  • In the study, the fatigue strength improvement and mechanism have been estimated by the Spot-Heating treatment on welded bead toes. For this, web-gusset specimens were made without residual stresses and the others with residual stresses imposed by Spot-Heating. The 4-point bending tests were performed in order to estimate the effect of spot-heating on fatigue strength and fatigue characteristics quantitatively for non load-carrying fillet welded joints subjected to pure bending. As a result of fatigue test, fatigue strength of As-Welded specimen for non load-carrying fillet welded joints subjected to pure bending has satisfied the grade of fatigue prescribed in specifications of korea, AASHTO and JSSC. As compare with As-Welded specimen and Spot-Heating specimen have increased about 20% for the fatigue strength at $7.7{\times}10^6$ cycles. The Spot-Heating by reformation of the residual stress on welded bead toes has greatly affected the fatigue crack propagation life, but has slightly affected the fatigue crack initiation life.

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Fatigue in People with Cancer : Concept Analysis (암환자 피로 : 개념 분석)

  • 이은현
    • Journal of Korean Academy of Nursing
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    • v.29 no.4
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    • pp.755-765
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    • 1999
  • Most people experience fatigue at some point in their lives, and they say the word ‘fatigue’ in their ordinary conversational speech. The ordinary word is used as a military or engineering term and has been studied in various different disciplines, such as ergonomics, physiology, psychology, medicine, and nursing. In spite of its widespread uses, however, fatigue has not been well defined. The term of fatigue Is thus often used with different meanings and is applied in diverse contexts that had led to a confusion of ideas. In people with cancer, fatigue is reported as a major distress. Despite the importance of fatigue in cancer patients, the phenomena of fatigue is poorly understood. Therefore, the purpose of the present study is to analyze the concept of fatigue in people with cancer. The process for the concept analysis was guided by Walker and Avant's conceptual analysis methodology. The identified attributes of fatigue in the present study were subjective feeling, lack of energy, sustenance, and multidimensions. The antecedents were cancer treatment and economic status. The consequences were decreased daily, vocational, leisure, and social activities, uncertainty, and difficulties in adjustment. Symptoms (pain, anorexia, and insomnia) and emotional disturbance were not clear whether they are antecedents or consequences. However, they are related with cancer related fatigue. Even though still in the beginning stage, instruments measuring cancer related fatigue have been developed by some nursing investigators.

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The fatigue analysis using cumulative damage rule (Miner's rule) for the welding areas of carbody structure (누적손상법(Miner's rule)을 이용한 철도차량 차체 용접부의 피로평가)

  • Kim, Kwang-Woo;Park, Geun-Soo;Park, Hyung-Soon
    • Proceedings of the KSR Conference
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    • pp.30-34
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    • 2007
  • Structural integrity of railway vehicles should last for a long period against various and continuous fatigue loadings, and the carbody structures of railway vehicle are manufactured by applying multiform welding types for each material. Since the most of cracks are occurred and proceeded at the vicinity of welding area during the lifetime of carbody structure, the fatigue strength evaluation for welding area of carbody structure should have been carried out. Rotem Company has evaluated lifetime and fatigue strength of carbody structure according to the fatigue analysis based on the international standard and/or inner-official regulation. This study introduces the fatigue analysis method that we have evaluated and calculated the damages for the welding areas of carbody structure under various fatigue loading conditions using cumulative fatigue damage rule(Miner's rule) to verify whether the cumulative damage does exceed unity. This study contains the fatigue test of specimens to derive stress-life relations(S-N curve), sub-modeling analysis and the calculation of cumulative damages under fatigue loading. The fatigue analysis verifies the welding area shall be capable of withstanding under fatigue loading, identifies how critical area shall be selected and presents the principles to be used for design verification.

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